The present invention is directed to integrated circuits and their processing for the manufacture of semiconductor devices. More particularly, the invention provides a method and system for calibrating measurement tools for semiconductor device manufacturing. Merely by way of example, the invention has been applied to establishing traceability of calibration standards. But it would be recognized that the invention has a much broader range of applicability.
Integrated circuits or “ICs” have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Current ICs provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of ICs. Semiconductor devices are now being fabricated with features less than a quarter of a micron across.
Increasing circuit density has not only improved the complexity and performance of ICs but has also provided lower cost parts to the consumer. An IC fabrication facility can cost hundreds of millions, or even billions, of dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of ICs on it. Therefore, by making the individual devices of an IC smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as each process used in IC fabrication has a limit. An example of such a limit is calibrating measurement tools for semiconductor device manufacturing.
Fabrication of custom integrated circuits using chip foundry services has evolved over the years. Fabless chip companies often design the custom integrated circuits. Such custom integrated circuits usually require a set of custom masks commonly called “reticles” to be manufactured. A chip foundry company called Semiconductor International Manufacturing Company (SMIC) of Shanghai, China is an example of a chip company that performs foundry services. Although fabless chip companies and foundry services have increased through the years, many limitations still exist. For example, in semiconductor industry, the calibration of measurement tools is very important. The measurement tools often need to be calibrated daily against high precision standards to make the tools work accurately and smoothly. For calibration standards, the International Organization for Standardization (ISO) often requires these standards being traceable to a worldwide acceptable origin. For example, the National Institute of Standards and Technology (NIST) in the United States is a worldwide acceptable origin.
According to certain conventional calibration techniques, a semiconductor company purchases a set of wafers that are used as calibration standards and traceable to a worldwide acceptable origin such as NIST. These wafers often are called golden wafers, and they are for example VLSI wafers. The golden wafers usually are very expensive, and the calibration processes often are consumable. In order to lower calibration costs, the semiconductor company often does not use the golden wafers for daily calibrations. Moreover, to simulate actual working conditions, the semiconductor company may select a set of frequently desired values, and calibrate the measurement tools at these special levels. But it is often difficult to obtain golden wafers with all these special levels at reasonable costs.
From the above, it is seen that an improved technique for calibrating measurement tools is desired.